# Redrives for most commercial engines.

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#### Vigilant1

##### Well-Known Member
-------- > Our redrives have the correct grade steel shaft for the job and precision machined. Resistant to breaking, cracking etc.

In over 10 years, none of our shafts have had damage.

They also fit tractor and pusher.

Id say theyre well designed redrives for high pulsing V-Twins.

View attachment 84080

Sold off eBay 950. Both Provision 4 & Provision 8. #### Armilite ##### Well-Known Member A 420 Single with some Mods, 34mm Carb, 11.0cr, better Air Filter and Exhaust, can make 34.62hp@5500rpm good for most Ultralights. The Highest I would turn them for plane use. #### cluttonfred ##### Well-Known Member HBA Supporter Agreed, I hope a Mod deletes those last two posts by Armilite as off-topic, but I am also confused because he also wrote earlier thin this thread, "All you have to do is write: info@aceaviation.co.uk and you will get all your answers. Ace has a Good Reputation. Belt Life really depends on the Person using it and Adjusting it. Old Style V-Belt/Cog Belt Drives were considered 200-250hrs, these new style Poly V Belts are a little better." #### John Penry-Evans ##### Active Member Agreed, I hope a Mod deletes those last two posts by Armilite as off-topic, but I am also confused because he also wrote earlier thin this thread, "All you have to do is write: info@aceaviation.co.uk and you will get all your answers. Ace has a Good Reputation. Belt Life really depends on the Person using it and Adjusting it. Old Style V-Belt/Cog Belt Drives were considered 200-250hrs, these new style Poly V Belts are a little better." I agree that belt life is up how the operator tensions it through its life. I know of one that has done over 400 hours with the same belt. Many with over 250 hours. Poly V-Belts are very robust. #### Armilite ##### Well-Known Member It's not cool to promote rival products in a supplier's thread. ============================================ Ace doesn't make a Belt Drive for any Rotax's. The guy who makes the Red Belt Drive Doesn't make any for the Honda/Briggs Engines. So they aren't in Competition. My Point was, these Honda/Briggs Singles and Big V Twins Engine's can make more HP than what they say their Belt Drive's are Rated for. #### Armilite ##### Well-Known Member Agreed, I hope a Mod deletes those last two posts by Armilite as off-topic, but I am also confused because he also wrote earlier thin this thread, "All you have to do is write: info@aceaviation.co.uk and you will get all your answers. Ace has a Good Reputation. Belt Life really depends on the Person using it and Adjusting it. Old Style V-Belt/Cog Belt Drives were considered 200-250hrs, these new style Poly V Belts are a little better." ========================================================== He started this thread with just a Photo and Titled it "Redrives for most Commercial Engines." did not even give the Brand Name, then sat back to see what People said about it. For a Honda/Briggs/Clone I think it's one of the better-built Belt Drives for them Style of Engines, but their HP Specs are fast falling behind these Honda/Briggs/Clone Singles and Big V Twins HP capabilities as I showed. They're also made in India, not Britain(UK). As more People here in the USA, Canada, Mexico look into these Cheap Honda, Briggs, 20+ Clone Engines and everybody wants more HP for their AirPlane, they may need to Upgrade their Product for that Market. I recommended their Belt Drives and these American Built Honda/Briggs/Clone Engines made by Vegas Carts, Bull Frog Racing, ARC Racing, NRC Racing, etc., just the other day to the Aerolite 120 Company made in Europe when they emailed me, as I have done to some other Ultralight Manufactures. So I have done more to Promote their Product then they have done here themselves. I have also given them and you People here an Honest Assessment of their Product. I was talking over 2 years ago before I retired in 2017 about a Distributorship of these Drives for here in the USA, which I turned down, account they had a 6 Month wait to get them. As I told them then, People don't want to wait 6 months for anything, today they want it yesterday. It's now been over 2 Years and they still haven't really broken into the USA/Canada/Mexico markets. There is over 350+ Airframe Manufacture's in the World per Kitplane Magazine. 350 x 25 Airframes = 8,750 a Year. 350 x 50 Airframes = 17,500 a Year. 350 x 75 Airframes = 26,650 a Year. 350 x 100 Airframes = 35,000 a Year. #### wsimpso1 ##### Super Moderator Staff member Log Member Looked at the web site, read the specs, still want to know a few things, and here seems to be a good place to get the info out: First, what is the rated gyroscopic reaction moment for this system? The prop is a very large inertia being spun and then there are yaw and pitch rotation from the airframe. Even if the drive's propshaft and bearings were not sized with this in mind, some simple math will produce loads due to unaccelerated loadings and to yaw and pitch rates. A trip to the bearing catalog would then tell us how long the bearings can be expected to live. Another set of junior level ME calcs will tell you if the prop shaft can be expected to live long (or not) under the same loads. Second, Do you have limits on inertia of engine side and prop side inertia with this system? These two inertia are important to keeping resonance out of the operating range, and I would expect that you might have set limits on one or both of these inertia. Third, what are the main resonant modes and their frequencies? With hundreds delivered, shouldn't you have at least run a torsional vibration survey on some popular engine and prop combinations to see that resonance is out of range and damaging vibration does not exist in the operating range? Billski #### John Penry-Evans ##### Active Member ========================================================== He started this thread with just a Photo and Titled it "Redrives for most Commercial Engines." did not even give the Brand Name, then sat back to see what People said about it. For a Honda/Briggs/Clone I think it's one of the better-built Belt Drives for them Style of Engines, but their HP Specs are fast falling behind these Honda/Briggs/Clone Singles and Big V Twins HP capabilities as I showed. They're also made in India, not Britain(UK). As more People here in the USA, Canada, Mexico look into these Cheap Honda, Briggs, 20+ Clone Engines and everybody wants more HP for their AirPlane, they may need to Upgrade their Product for that Market. I recommended their Belt Drives and these American Built Honda/Briggs/Clone Engines made by Vegas Carts, Bull Frog Racing, ARC Racing, NRC Racing, etc., just the other day to the Aerolite 120 Company made in Europe when they emailed me, as I have done to some other Ultralight Manufactures. So I have done more to Promote their Product then they have done here themselves. I have also given them and you People here an Honest Assessment of their Product. I was talking over 2 years ago before I retired in 2017 about a Distributorship of these Drives for here in the USA, which I turned down, account they had a 6 Month wait to get them. As I told them then, People don't want to wait 6 months for anything, today they want it yesterday. It's now been over 2 Years and they still haven't really broken into the USA/Canada/Mexico markets. There is over 350+ Airframe Manufacture's in the World per Kitplane Magazine. 350 x 25 Airframes = 8,750 a Year. 350 x 50 Airframes = 17,500 a Year. 350 x 75 Airframes = 26,650 a Year. 350 x 100 Airframes = 35,000 a Year. #### John Penry-Evans ##### Active Member Looked at the web site, read the specs, still want to know a few things, and here seems to be a good place to get the info out: First, what is the rated gyroscopic reaction moment for this system? The prop is a very large inertia being spun and then there are yaw and pitch rotation from the airframe. Even if the drive's propshaft and bearings were not sized with this in mind, some simple math will produce loads due to unaccelerated loadings and to yaw and pitch rates. A trip to the bearing catalog would then tell us how long the bearings can be expected to live. Another set of junior level ME calcs will tell you if the prop shaft can be expected to live long (or not) under the same loads. Second, Do you have limits on inertia of engine side and prop side inertia with this system? These two inertia are important to keeping resonance out of the operating range, and I would expect that you might have set limits on one or both of these inertia. Third, what are the main resonant modes and their frequencies? With hundreds delivered, shouldn't you have at least run a torsional vibration survey on some popular engine and prop combinations to see that resonance is out of range and damaging vibration does not exist in the operating range? Billski Ace Aviation Redrive design calculations: To the customer (Or Wsimpso1) -------- You may one day be using the redrive on a permit aircraft and get a request for calculations from an approval body. This means my initial rough numbers need updating to suit the revised structural design of the redrive. It assumes a 3” or 75mm deep propeller boss and 1620mm overall diameter. To cover the liability issue I’ve gone over the top with the propeller out of balance at 10 grams, (.352 ounce) this will cover loss of a tip for instance from a stone, and a pilot would soon land his machine at the earliest opportunity with 56.61 kilos of force shaking his aircraft around, provided the engine mounting coped. To recap:- Up to 5 times 10 to the eighth power cycles, allowable stress in 6082 (T6) alloy at 280N/mm² is the yield times 0.38. Yield is 280N/mm², so 280x0.38 is 106.4N/mm²; this is the ‘fatigue limit’ limit we should not pass. http://www.roymech.co.uk/Useful_Tables/Fatigue/Fatigue.html 5 x 10 to the eighth is a life of 4,167 hours at 2,000rpm. At 100 hours a year this is 41.67 years. Belt pull check:- use Rotax 503 power levels:- 50Nm torque on 100 dia pulley = 50N/0.05 radius = 1kN or 102kgf Acts at 44.8mm away from C/L of plate; B.M = 1000x0.0448=44.8Nm or 44,800Nmm Add centrifugal force; assume 10 grams out of balance propeller (damage to tip on departure) http://www.calctool.org/CALC/phys/newtonian/centrifugal Radius: 810 2500rpm centrifugal force = 555.165N (kg.m/s²) or 56.61kgf Acts at maximum 144.7m away from backplate so added BM = 555.165x0.1447m or 80.33Nm, or 80,332Nmm Total BM = 80.33 + 44.8 = 125.13Nm = 125,130 Nmm Taking moments about prop boss assembly and redrive backplate 1) Max BM at narrowest point of plate= 144.7/53x125.13=341.634 Nm 2) Max unsupported BM at base of prop boss = 144.7/43x125.13=421.07 Nm 1) Section Modulus Z = BD²/6 or 2x32 x 16²/6 = 2730mm³ Material stress = BM/Z. = 125,130/2730 = 45.83N/mm² 2) Section Modulus = 96 x 16²/6 = 4096mm³ Material Stress = 125,130/4096 = 30.55N/mm² Bearings The way bearings are rated is full load for one million revolutions, or about 6-7 hours running at full 2,500 propeller revs, however… The belt pull at full throttle is around 90 kilos, tension around 90kilos and centrifugal force 5.24kilos so under 200kilos total at worst full throttle, at half throttle cruise maybe half that figure. Capacity of the bearing is 11.2kN or 1,142 kilograms each, as there are two bearings total capacity of redrive bearing assembly is 2,284 kilograms. So bearings are eleven times stronger than they need to be, the 6005 -2RS (rubber shielded) are totally sealed and are sheltered inside the assembly so doubt contamination is an issue. As you can see, stress imposed is under one half of the maximum the alloy can accept; however as deflection of the plate causes misalignment of the pulleys, this is a desirable situation. Hope that this explains a few things. #### John Penry-Evans ##### Active Member ============================================ Ace doesn't make a Belt Drive for any Rotax's. The guy who makes the Red Belt Drive Doesn't make any for the Honda/Briggs Engines. So they aren't in Competition. My Point was, these Honda/Briggs Singles and Big V Twins Engine's can make more HP than what they say their Belt Drive's are Rated for. We have not seen much call for redrives for these older 2 stroke Rotax engines. When any inquiry comes into us for Rotax 2 stroke redrives. I ask for Cad drawings of the engine casework. No one has come even close to giving us those yet. I get rough drawings. That`s not good enough. Too risky for production. Wrong Sir: We custom make our redrives for commercial engines as per requirement. So we cover all hp levels. Really depends on what the customer wants. My advise is then recommended. #### wsimpso1 ##### Super Moderator Staff member Log Member Ace Aviation Redrive design calculations: To the customer (Or Wsimpso1) -------- You may one day be using the redrive on a permit aircraft and get a request for calculations from an approval body.... Hope that this explains a few things. That is all good info. You looked at the bearings from a foreseeable failure perspective and for adequate life of them under normal and unusual circumstances. While I had hoped that you might have designed the bearings to last a long time under nominal loadings, that covered zero of my three questions. When a question is asked and the answer comes nowhere close to addressing the question, many of us suspect that the respondent either does not understand the question, or that the respondent is being evasive for any number of reasons. Let's just assume you misunderstood my questions. Rest assured that my questions arise from my history as a successful powertrain engineer who has been heavily involved in vibration management in cars/trucks and in an airplane project. I am no dilettante here, the questions come out of real world circumstances, and the airplane cases are real. The first question was about allowable gyroscopic moments fed in at the prop hub - the inertia of the prop spun at operating speed and then under yaw and/or pitch rotation. People can do snap rolls, spins, gyroscopics, spirals, or just plain moving the elevator or rudder sharply for short intervals (like clearing the envelope for flutter). These pitch and yaw rotations combined with prop inertia and rotation cause gyroscopic moments that must be carried by the prop hub, prop shaft and the bearings mounting the prop shaft. I kind of expected that you would have either established limits on prop inertia or rotation rates or on total moment based upon propshaft characteristics and propshaft bearing limits... The second question was about mass moment of inertia limits on flywheels and propellors, because you might have found unacceptable resonance with certain combinations of engine and propellor inertia. I kind of expected that you would have looked at torsional resonance and established limits on inertia values to avoid resonance modes and frequencies that are in or near the operating range... The last question was related to the second question, and was about computed torsional vibration modes and frequencies for common engines and props to see that these damaging resonances are safely out of range. I kind of expected some due diligence here to know that common engine and prop combinations would not result in resonance. Billski #### Factory-Fit ##### Member That is all good info. You looked at the bearings from a foreseeable failure perspective and for adequate life of them under normal and unusual circumstances. While I had hoped that you might have designed the bearings to last a long time under nominal loadings, that covered zero of my three questions. When a question is asked and the answer comes nowhere close to addressing the question, many of us suspect that the respondent either does not understand the question, or that the respondent is being evasive for any number of reasons. Let's just assume you misunderstood my questions. Rest assured that my questions arise from my history as a successful powertrain engineer who has been heavily involved in vibration management in cars/trucks and in an airplane project. I am no dilettante here, the questions come out of real world circumstances, and the airplane cases are real. The first question was about allowable gyroscopic moments fed in at the prop hub - the inertia of the prop spun at operating speed and then under yaw and/or pitch rotation. People can do snap rolls, spins, gyroscopics, spirals, or just plain moving the elevator or rudder sharply for short intervals (like clearing the envelope for flutter). These pitch and yaw rotations combined with prop inertia and rotation cause gyroscopic moments that must be carried by the prop hub, prop shaft and the bearings mounting the prop shaft. I kind of expected that you would have either established limits on prop inertia or rotation rates or on total moment based upon propshaft characteristics and propshaft bearing limits... The second question was about mass moment of inertia limits on flywheels and propellors, because you might have found unacceptable resonance with certain combinations of engine and propellor inertia. I kind of expected that you would have looked at torsional resonance and established limits on inertia values to avoid resonance modes and frequencies that are in or near the operating range... The last question was related to the second question, and was about computed torsional vibration modes and frequencies for common engines and props to see that these damaging resonances are safely out of range. I kind of expected some due diligence here to know that common engine and prop combinations would not result in resonance. Billski Encountered many such repeat queries in thirty years of structural design; the questioner will just lazily bat this back no matter what information Ace Aviation provide, there's a sad aspect to human nature that enjoys watching folk jump around as they tug their leash, and waste a busy (and honest) man's time. Sometimes the motive is good and based on proper checking, but the tone here belies that. The questions need to be sieved in relevance to the application in case they are spurious; an aerobatic aircraft will, if the builder/pilot values his life and the inspection regime is in place will ALREADY have a full set of design calculations in place, with the propeller precession etc accounted for; this will be backed up by load testing at the propeller hub. Performing such checks on the engine/redrive assembly will answer the questions and also reveal the above answer demands as a waste of time, intended only to demonstrate how clever the questioner is... There are literally millions of mounting, configuration, prop diameters, pitch and numbers of blades; it is incumbent on the experimental aircraft builder to determine all this, and ground run the thing after load testing; Some combinations will fail testing; that's not Ace Aviation's fault. They make a pretty beefy reduction drive, and if the prop loads and reactions are sufficient to break that, such forces will already have broken the airframe or had the pilot grateful for investing in a recovery parachute. Aerobatic aircraft design is far more onerous than simple kit runabouts, so attacking the component manufacturer for not producing those millions of guessed combinations doesn't show good faith in my view. My original reduction design, upon which the current variations are based was set up for a 40hp tuned Briggs, not sure where 28hp came from but once the ideal prop, pitch etc was arrived at the machine climbed at a similar rate when equipped with a 39hp Rotax 447, despite the power unit being around ten kilos heavier. Since a 447 output is 39hp, it would appear reasonable to moot around 35hp at the prop for the four stroke. The Briggs was efficient and could cover 250 miles burning 23.6 litres in 3.75 hours; one trick the USA tuners know (and I didn't until too late) is that the cast iron cam requires steel core reinforcing to cope with higher lift rockers, stronger valve springs and higher lift profile. That came home to roost when the cam broke at 120 hours and, being an engineer but lousy pilot, the chosen landing spot was a bog. The trike was rolled into a ball and snapped a prop blade. Precision Cams (Mike Edwards) make both billet and steel reinforced cams for350 and $250 respectively so do fit that spec. if following that path. That reduction drive (and original belt) was removed from the totalled trike after the crash, fitted to a new engine and flown for another twenty hours without any evidence of deterioration; belt was like new and showed zero sign of wear or slippage, despite having hot exhaust runners wrapped around it. A new reduction is now performing stirling work on the latest project, this is a 800cc 61hp fuel-injected ATV motor (Rotax copy by Gaokin), spinning at up to 6,250 rpm on a 2.2:1 reduction setup, two upgrades were incorporated, a 19 row pulley/belt set up from 14, and the bolts clamping prop hub to large pulley body increased to 8mm from 6mm. So far the only test result not expected was a little belt dust evident after continuous full throttle climbs to 4000 feet, this prompted another check of the belt tension calculations, which are now upped to 20Nm torque setting on the eccentric shaft centre bolt held and clamped to hold the setting. I was just being lazy not to work it out properly as per page 34 of the Contitech design manual, worth a builder downloading it and working through those simple formulae. Experimental aircraft are just that, even Doctor Gratton at UK Brunel Uni's aeronautical facility was staggered to see inertial resonance set a composite propeller almost in flames, so demanding resonance calculations is one thing, but my strong preference is test, test and test again. And John at Ace Aviation is a very honest Brit by the way, so sneering at the product being made in India isn't cool; I found the machining standard excellent, it's probably being done on Colonial era British machine tools... #### Vigilant1 ##### Well-Known Member Lifetime Supporter My original reduction design, upon which the current variations are based was set up for a 40hp tuned Briggs, not sure where 28hp came from but once the ideal prop, pitch etc was arrived at the machine climbed at a similar rate when equipped with a 39hp Rotax 447, despite the power unit being around ten kilos heavier. Since a 447 output is 39hp, it would appear reasonable to moot around 35hp at the prop for the four stroke. Just an estimate based on your stated fuel consumption of about 7-7.5 l/hr "when driven hard." Per above: Fuel consumption: On one long trip he burned 6.3 l/hr (= 1.7 GPH). Also says it " only burns 7-7.5 litres per hour (1.85 - 2 GPH) even when driven hard." If we assume a BSFC for this little engine of about .43 lbs/hp/hr, that would mean an output of up to 28 HP "if driven hard" and 23-24 HP continuous on his long trip. It's quite possible that "driven hard" doesn't mean "all she would do," but it's not likely that this small air-cooled carb-fed engine will make 35 HP (esp at the prop) on 7.5 l/hr (.34 lb/hr/hp). Thanks for sharing the information on your project. BJC #### pictsidhe ##### Well-Known Member Factory fit. Are you saying that anyone wanting to use an Ace drive should buy one, measure its dimensions, take a guess at the materials used then calculate what MOI propeller it can safely swing and meet, say, FAR 23.371? Then do their own TV calculations or testing to check it won't self destruct from that aspect? I know that 103s and many other aircraft don't need to meet part 23, but it's a sensible set of regulations to compare against. Thanks, I'd rather scratch design my own redrive than blow$700 on a drive that appears to be lacking in both design calculations and manufacturer testing. It may well be that it would be suitable for me, but it's $700 down the toilet if not. The fact that people aren't having early failures does suggest that the Ace drives are worth a close look. Your belt dust report is really not encouraging, though. You'll notice that Rotax specifies a max MOI for it's gearboxes. Is it really unreasonable to expect other redrive manufacturers to do likewise? This discussion has prompted me to try again and get a figure for the elasticity of PK belts to investigate TV. I'm having trouble getting that information from the manufaturers. I may end up measuring it myself. #### Vigilant1 ##### Well-Known Member Lifetime Supporter My original reduction design, upon which the current variations are based was set up for a 40hp tuned Briggs, not sure where 28hp came from but once the ideal prop, pitch etc was arrived at the machine climbed at a similar rate when equipped with a 39hp Rotax 447, despite the power unit being around ten kilos heavier. Since a 447 output is 39hp, it would appear reasonable to moot around 35hp at the prop for the four stroke. The Briggs was efficient and could cover 250 miles burning 23.6 litres in 3.75 hours; one trick the USA tuners know (and I didn't until too late) is that the cast iron cam requires steel core reinforcing to cope with higher lift rockers, stronger valve springs and higher lift profile. That came home to roost when the cam broke at 120 hours and, being an engineer but lousy pilot, the chosen landing spot was a bog. The trike was rolled into a ball and snapped a prop blade. Precision Cams (Mike Edwards) make both billet and steel reinforced cams for$350 and \$250 respectively so do fit that spec. if following that path.
Again, thanks for the firsthand information. A few questions:
1) Did you ever make measurements of the CHTs you were running (at top of climb, in cruise, etc)? In general, we typically see that aluminum-head air cooled 4-stroke engines require about 30-33cc per continuous (reliable) hp, just based on limitations of these heads to keep up with the heat shedding requirements if pushed harder than that. If using that rule of thumb, we'd expect the Vanguard 627cc engine to be good for about 19-21 continuous HP, but you clearly were going above this level. If you recorded CHT numbers, where was the thermocouple located?
2) If looking at an industrial engine to produce 25-30 HP, would you go with the Vanguard 627 again, or would you start with a different base engine? Many folks here have considered the B&S or Vanguard 810cc engine, which is a nice displacement for achieving 25-28 HP in stock trim and near-stock max RPM (3600), but they only come in a vertical shaft model, so that increases the complexity of using it.
3) Your modifications below, from a post at your YouTube video: Would you do things differently, and what approx was the cost? Thanks.
Raised compression by special pistons and stronger connecting rods, rather than skimming the heads.
- Special camshaft
( He wrote this comment: if you do go this route make sure you fit a reinforced camshaft, mine broke after 160 hours. Precision Cams do both reinforced and billet versions)
- Packers to valve springs to allow higher revs
- Stainless exhaust valves to withstand heat
- Roller tipped higher ratio valve rocker levers, 1.5 ratio instead of 1.1
- Bigger carb off the 990cc model but with jet kit for operation at 5000' (Briggs accessory)
- Open up inlet manifold to suit bigger carb butterflies
- Longer tuned length exhaust tubes 29mm bore.
- NGK Iridium plugs
- Machined 3 kilos off the flywheel, then balanced and spin tested.

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#### pictsidhe

##### Well-Known Member
Factory Briggs 627s are rated up to 23hp. They have some cooling capacity in reserve to cope with filthy fins and general abuse. I don't know how much, yet. I am planning to use one, and would like to get north of 30hp. I am half expecting to need to add internal oil cooling to achieve my target. Yes, a bigger oil cooler, too.

#### Factory-Fit

##### Member
First off cooling:-
Tests were made directly above an airfield with multiple runways in case things went bang. The Briggs chosen is not the common USA red cowled version but the deeper fan/black cowl that the Japanese introduced; mine was from Europe. Have photos of the two versions after ordering a replacement and getting the wrong one...
Always fit strip braces across the fan if you delete the mesh screen, I didn't like the thought of a rotating screen within hand's reach so attached it static to the outer case and the fan, denuded of its bracing, expanded and shattered.

Sensors were standard Rotax 447 type plug CHT rings, at no stage did the CHT's get above 180°C even in a continuous climb to 7000 feet, YouTube video is somewhere on my channel.

Puzzled at the 'math' from one poster of fuel burn and horsepower calculations; a trike needs only 20-25hp to stay level, mine climbed at 700 feet per minute full throttle, then was backed to half throttle to cruise at 58mph for 3.75 hours, it burned 23.6 litres of fuel. Appears sums by poster being done correctly but then miss the point that a long term cruise is conducted at less throttle, hence after calculating fuel burn he thinks it makes less power at all times?

One fault all the Vanguards appear to have is the prop forces are quite easily handled by the reduction drive structure, but cause the engine casing itself to weep oil at joints, eventually had to use the longest Allen bolts it would take and lockwire them, Al Hodge tunes these and has switched over to no gasket and Honda Bond, which means changing the crankshaft end float shim for thinner. Basically the redrive structure is a lot stronger than what it's bolted to, PLUS I rate load-testing above calculations, the fatigue sums were only done to check as alloys have no elastic limit under which fatigue is not present, unlike steel.

I would have made a new case from billet but it has oil galleries and the pump inside, too complex, reckon a better solution could be to bracket the redrive backplate off separate mounts down to the base fixing, and up to the heads area. The crankcase is big and possibly needs internal stiffening to stop oil weeps, the 810 vertical shaft suffers from this too; try researching on YouTube and agricultural websites and forums.

The 627cc small block is a lot lighter than the 990cc Big Block; it's strong enough to output 35hp but needs a stronger camshaft, as before, see Precision Cams, although would avoid their super strong valve springs, one 2mm shim under new stock springs proved enough at 4500rpm.

The belt dust was only because I was too conservative with tension; once the Contitech standard formulas were followed tension was raised to 200kgf, shared between two sides, still well within bearing capacity. This is calculated using Sine of belt wrap angle on small pulley, kiloWatts transmitted and number of grooves on PK section. they give a handy shaded graph of suitable belt types for each combo and rpm of small pulley.

As before my redrive is 'crash tested' and was reused, being pretty much the sole survivor of that incident; belt life I simply cannot answer as it showed insufficient wear after abuse including being splattered with oil and scrubbed clean, but it survives under truck bonnets and on quarry applications quite well...

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