Can i use two bearing blocks (for a 20mm shaft) as swing arm mounts?

[Master Hack]

You'll be much happier with that. A lot easier.
The bearing "blocks" will work, but its a lot more work and won't be as durable.
Ball bearings get a little cranky when they only oscilate the same few degrees over and over. That with some shock loading...

 

[MoTiJo2023]

You'll be much happier with that. A lot easier.
The bearing "blocks" will work, but its a lot more work and won't be as durable.
Ball bearings get a little cranky when they only oscilate the same few degrees over and over. That with some shock loading...

I just thought about it a bit and i need a jackshaft, because the enginee would stick out too much if i dont use a jackshaft, not that big of a problem- i can use the bearing blocks and the shaft i have for that.
Im using a 200cc honda gx clone (cost me 100€ brand new and runs perfect) but because it obviously is a bit cheaper, it has a bit more engine vibration than a expensive engine has. Do you think i can use these rubber enigne mounts, or will it just throw the chain often if i use them ?

 

[bob58o]

I don’t think Denny will like those mounts.
I have no experience with them. I reckon some square tubing ought to be ok if thick enough not to squish, that’s only if you need to raise it up.
If it shakes at 3000 RPM, go 4000 RPM.
If it wobbles at 36 mph, go 45!

 

[Denny]

The rubber mounts will not stay tight and allow your engine to slide and move around. Good call Bob!

 

[Rat]

I just thought about it a bit and i need a jackshaft, because the enginee would stick out too much if i dont use a jackshaft, not that big of a problem- i can use the bearing blocks and the shaft i have for that.
Im using a 200cc honda gx clone (cost me 100€ brand new and runs perfect) but because it obviously is a bit cheaper, it has a bit more engine vibration than a expensive engine has. Do you think i can use these rubber enigne mounts, or will it just throw the chain often if i use them ?
View attachment 144851

Those mounts are for STATIONARY EQUIPMENT ONLY!!!
You put those on a kart or mini bike and you will spend more time unFuxking your chain than riding.
There is absolutely no way to isolate the engine without causing movement problems.

Before You throw automotive engines as an argument, DRIVESHAFT with slipjounts and movement figured into the design.

Before you throw a Harley in as argument, the transmission is hard mounted separate from the engine block and either connected to it by belt or chain, AGAIN movement is figured into the design so the use a 3" wide belt or a double roller chain so the amount the engine moves on its bushings is essentially being restrained by running gear that doesn't move before being transferred to the wheel.

 

[MoTiJo2023]

Those mounts are for STATIONARY EQUIPMENT ONLY!!!
You put those on a kart or mini bike and you will spend more time unFuxking your chain than riding.
There is absolutely no way to isolate the engine without causing movement problems.

Before You throw automotive engines as an argument, DRIVESHAFT with slipjounts and movement figured into the design.

Before you throw a Harley in as argument, the transmission is hard mounted separate from the engine block and either connected to it by belt or chain, AGAIN movement is figured into the design so the use a 3" wide belt or a double roller chain so the amount the engine moves on its bushings is essentially being restrained by running gear that doesn't move before being transferred to the wheel.

Yes, you are right, but what if i use these rubber bushings/mounts that look like the swingarm busings, for engine mounts?:

They are built the same as the swingarm mounts, they are just a bit thicker, they are even mounted in the same direction as the swingarm mounts. My s51 moped has its engine sitting inside of these bushings from factory, the engine is only moving up and down a bit because i need to replace the bearings, they are worn out, not left or right movement and it has never thrown the chain. I can do bournouts with my moped, jump it or do donuts in the snow, i can see the engine bouncing up and down a bit but is has never thrown a chain.

 

[Rat]

Yes, you are right, but what if i use these rubber bushings/mounts that look like the swingarm busings, for engine mounts?:
View attachment 144872
They are built the same as the swingarm mounts, they are just a bit thicker, they are even mounted in the same direction as the swingarm mounts. My s51 moped has its engine sitting inside of these bushings from factory, the engine is only moving up and down a bit because i need to replace the bearings, they are worn out, not left or right movement and it has never thrown the chain. I can do bournouts with my moped, jump it or do donuts in the snow, i can see the engine bouncing up and down a bit but is has never thrown a chain.

If your bearings are shot then you replace the bearings. WTF is wrong with you!?!?

You do you, and when (not if) you regret it, do not come here whining about it because you have been more than adequately told why it can not be done and should not be done.

If your engine vibrates that much then either tune it better, or replace it. Unless something is bent, proper tuning knocks a solid 90% of the vibrations out of just about any engine but no less than 75% for even the worst turd available to those with a weak wallet

Fact is You only get zero vibrations by going electric.

I've known a few idiots That figured skinning a truck tire to toss under their engine like a pad...

one of them almost didn't live to regret it when all was over.
A truck tire is harder rubber than any of those pathetic bushings you insist on trying to use.

 

[MoTiJo2023]

If your bearings are shot then you replace the bearings. WTF is wrong with you!?!?

You do you, and when (not if) you regret it, do not come here whining about it because you have been more than adequately told why it can not be done and should not be done.

If your engine vibrates that much then either tune it better, or replace it. Unless something is bent, proper tuning knocks a solid 90% of the vibrations out of just about any engine but no less than 75% for even the worst turd available to those with a weak wallet

Fact is You only get zero vibrations by going electric.

I've known a few idiots That figured skinning a truck tire to toss under their engine like a pad...

one of them almost didn't live to regret it when all was over.
A truck tire is harder rubber than any of those pathetic bushings you insist on trying to use.

Nothing is wrong with me, i just found out that the bushings are worn (after 40years of use) out a few weeks ago and ignored it because it worked just fine) don't worry, i'll replace them).
Im not gonna complain if its not working, i bet it will work fine the way i'll do it. (and you dont complain when i get actually working.)
The engine is not having that much vibration, i just thought it would be nice to have rubber engine mounts.
Another fact: I could get polyamide engine mounts (polyamide is harder than rubber)
The reason why im not going electric is because it would be too easy for me and because you have no problems with e- motors- where is the fun?

 

[MoTiJo2023]

If your bearings are shot then you replace the bearings. WTF is wrong with you!?!?

You do you, and when (not if) you regret it, do not come here whining about it because you have been more than adequately told why it can not be done and should not be done.

If your engine vibrates that much then either tune it better, or replace it. Unless something is bent, proper tuning knocks a solid 90% of the vibrations out of just about any engine but no less than 75% for even the worst turd available to those with a weak wallet

Fact is You only get zero vibrations by going electric.

I've known a few idiots That figured skinning a truck tire to toss under their engine like a pad...

one of them almost didn't live to regret it when all was over.
A truck tire is harder rubber than any of those pathetic bushings you insist on trying to use.

I just thought about it a bit and now i know how i'll build it.

Its important that the jackshaft spins at the same RPM as the engine, so the centrifuigal clutch engages.
The belt will always be tightened by a spring and a belt tensioner, belt wont jump off if the engine vibrates on mounts.

 

[Master Hack]

Won't work for several reasons

 

[MoTiJo2023]

Won't work for several reasons

Tell me why

 

[Master Hack]

Well, We already covered the rubber mounts, so I'll leave that except to say. You will have X number of pound feet of torque pulling on that chain, trying to bring the engine and jackshaft closer together, and without solid mounts it will succeed.
#2 When the chain and swing arm have different pivot points the chain tension will vary as the swing arm travels along its arc. So you will play hell trying to keep the chain on.
That can be kept to a minimum by placing the two pivot points in the same plane. a chain tensioner might help.
Do yourself a favor and look at pics and see what others have done. Its done that way cuz it works.
(well don't look at my s**t)

 

[MoTiJo2023]

Well, We already covered the rubber mounts, so I'll leave that except to say. You will have X number of pound feet of torque pulling on that chain, trying to bring the engine and jackshaft closer together, and without solid mounts it will succeed.
#2 When the chain and swing arm have different pivot points the chain tension will vary as the swing arm travels along its arc. So you will play hell trying to keep the chain on.
That can be kept to a minimum by placing the two pivot points in the same plane. a chain tensioner might help.
Do yourself a favor and look at pics and see what others have done. Its done that way cuz it works.
(well don't look at my s**t)

Those are problems that i can easily solve!
#1: build strong jackshaft mount.
#2: Get the right pivot point and build a diy spring chain tensioner.
I have already bought all the parts, so its time to figure out if im right (i bet i am) or if im not and it wont work!

 

[Rat]

Those are problems that i can easily solve!
#1: build strong jackshaft mount.
#2: Get the right pivot point and build a diy spring chain tensioner.

The correct pivot point for rear suspension has been proven already... the pivot axis must be directly parallel or as close as possible to the output/counter gear without causing bind.
This is partly why dirtbikes use a steep swingarm angle with a slider to catch the chain slack created. The other reason is the same reason why you can not safely use rubber mounts, under load the engine will try to draw what ever its attached to by chain closer... street bikes tend to squat where the torque alone compresses the suspension. Dirtbikes are the opposite the torque actually forces the suspension to fully extend to the point it behaves like a hardtail which is ideal for maximum traction in the soup.
If the counter gear is above, the chain loosens as the suspension compresses; If below it tightens (or binds) which is far worse.

In a perfectly engineered design the best method to eliminate any and all necessity for any form of chain guid or tensioner assembly would be found in the swing arm axis also being the jackshaft because that's the only point of constant distance for the suspension travel.

I have already bought all the parts, so its time to figure out if im right (i bet i am) or if im not and it wont work!

I'm all for doing what others say cannot be done, but the line drawn is the one that comes with mechanical competence and solid logic as to exactly why it can not be done. When there is no legitimate basis for "You can't do that" then there's room to challenge the status quo, and I will full force and I'm damn good at doing what cannot be done.

In your case it's just plain hubris, ignorance, and stupidity; You will find out the hard way that the collective knows more than you.

 

[Master Hack]

I'm done! Good luck! Keep us posted on your progress!

 

[Rat]

I'm done! Good luck! Keep us posted on your progress!

Mah iggy bin is about to get a new inductee

 

[MoTiJo2023]

The correct pivot point for rear suspension has been proven already... the pivot axis must be directly parallel or as close as possible to the output/counter gear without causing bind.
This is partly why dirtbikes use a steep swingarm angle with a slider to catch the chain slack created. The other reason is the same reason why you can not safely use rubber mounts, under load the engine will try to draw what ever its attached to by chain closer... street bikes tend to squat where the torque alone compresses the suspension. Dirtbikes are the opposite the torque actually forces the suspension to fully extend to the point it behaves like a hardtail which is ideal for maximum traction in the soup.
If the counter gear is above, the chain loosens as the suspension compresses; If below it tightens (or binds) which is far worse.

In a perfectly engineered design the best method to eliminate any and all necessity for any form of chain guid or tensioner assembly would be found in the swing arm axis also being the jackshaft because that's the only point of constant distance for the suspension travel.


I'm all for doing what others say cannot be done, but the line drawn is the one that comes with mechanical competence and solid logic as to exactly why it can not be done. When there is no legitimate basis for "You can't do that" then there's room to challenge the status quo, and I will full force and I'm damn good at doing what cannot be done.

In your case it's just plain hubris, ignorance, and stupidity; You will find out the hard way that the collective knows more than you.

What if-
i tell you that i have already gotten such a setup to work?
I used a honda gcv 135cc Lawnmower engine on a gokart, because the shaft is not horizontal i had to get a 90° gearbox that has a sprocket at the output shaft.
This is the gearbox i used:

(its a peerless 700 lawntractor gearbox)


This picture is the belt clutch setup, on minibike im not gonna use a belt clutch, imma use a always tight belt (spring tensioner) and a centrfuigal clutch on the jackshaft.
The lawnmower engine is sitting on rubber engine mounts, you cant see them on the picture.
This setup worked perfectly (it does not matter if you use a gearbox (90°) or a straight jackshaft with this belt setup for rubber engine mounts)
The problem where the engine pulls the chain has already been taken care of, because it will pull on the belt under load and belt is spring tensioned.

 

[Master Hack]

How is that even remotely similar to this other thing?

 

[MoTiJo2023]

How is that even remotely similar to this other thing?

Its the same principle as the ''the other thing'', it just uses a gearbox instead of a jackshaft.
Engine sits on rubber bushings, belt is the thing that keeps the transmission turning and the chain wont pop off because its not directly connected to the engine thats gonna move a bit becasue of the bushings.
Its kinda the same and not the same.
(I know a kart is not a minibike and there is a 90° gearbox instead of a jackshaft, but ''the thing'' im talking about is the same, its about the fact that you can put a engine on rubber monts without having your chain jump off.)

 

[Master Hack]

Yer gonna do it, so just do it! what do ya need us for? You obviously know more than us. We never claimed to be experts anyway.
Not interested in getting into a pissing match!